LAMELLIBEANCHTATA OF THE LOWER MAELS. 137 



from the base of the shell to the hinge than the opposite side. Surface of the 

 valves marked on the posterior side with strong rounded ribs, but appar- 

 ently not extending quite to the crest of the umbonal ridge, the anterior 

 side of the valve being marked only by irregular concentric striae. In- 

 terior margin of the shell crenulate on the ribbed part of the valve, but 

 apparently not beyond it. From the appearance of internal casts the car- 

 dinal teeth have not been particularly strong, but the laterals on the anterior 

 side have been large and thick, with considerable height; postero-laterals 

 somewhat smaller. Muscular imprints large. In one large specimen they 

 are faintly marked, but in another smaller individual they have been quite 

 deep on the anterior side. On the posterior side the shells seem to have 

 been impressed from the margin of the imprints to near the beaks. 



This shell is next to the largest species of Cardium known in the Cre- 

 taceous of New Jersey. The internal casts somewhat resemble those 

 which I have referred to (7. EufauUnsis Conrad, but they may be distin- 

 guished by the total absence of ribs on the central and anterior parts of 

 the valve and by the want of crenulations left on the cast by the ribs 

 along the junction of the valves; also by the curvature of the beaks toward 

 the anterior side of the shell, whereas those of that species are straight. 

 The inequality in the height of the anterior and posterior sides of the shell 

 will also serve as a distinguishing mark. It is closely allied to C. (Pachycar- 

 dium) Spillmani Conrad, from Tippah County, Mississippi, but I cannot think 

 it is identical, as it answers neither to the description nor figure given of that 

 species. The type of that species figured was badly crushed and distorted, 

 but it shows very distinctly that it had been a broader shell, with broad, 

 flattened ribs on the posterior side, which were separated by flattened inter- 

 spaces of more than equal width. I have been unable to see an authentic 

 specimen of (7. Spillmani with which to compare it, however. This shell is 

 not uncommon in New Jersey, and so far I never have found it labeled, 

 except in the collection of the Academy of Natural Sciences of Philadel- 

 phia, where it is marked in Mr. Gabb's handwriting as ^'possibly not Spill- 

 mani." As both Mr. Gabb and Mr. Conrad frequently handled the speci- 

 mens, I think had they considered it identical it would have been so marked. 

 Still it is difficult to conceive why they did not describe it. 



